Migrations Carol Wolf CS 396X

ISBNTitleAuthorImage EmmaAustenemma.jpg Oliver TwistDickenstwist.jpg HamletShakespearehamlet.jpg Relational Databases  A relational database consists of a number of different tables.  Each table is like a two dimensional array.  The columns show the attributes (fields) of the data.  The rows each store information about a single item.  The first column stores the ISBNs for each book.  The first row stores information about Emma by Jane Austen.

Creating a table in Rails  InstantRails supplies an empty database called development.sqlite3.  A table is created by a migration. ruby script/generate scaffold book isbn:string author:string title:string  The resulting table will be called books and have the three columns named, above each holding a string.  It will also have several other columns supplied by Rails.  A primary key called id of type integer.  Timestamps of type date.  Rails gives the resulting Ruby program a name beginning with a timestamp, _create_books.rb.

Migration file to create a new table. class CreateBooks < ActiveRecord::Migration def self.up create_table :books do |t| t.string :isbn t.string :author t.string :title t.timestamps end def self.down drop_table :books end